Four-wheel drive vehicles are equipped with a transmission to convert the driving force of an internal combustion engine, and a transfer arrangement to distribute the power or driving force input from the transmission to two output shafts. Some four-wheel drive vehicles are equipped with a center differential to permit the two output shafts to turn at different speeds.
Examples of four-wheel drive wheels of the above type are illustrated by JP Laid-Open No. H02-204133, JP Laid-Open No. H05-42838, JP Laid-Open No. H06-17889, and JP Laid-Open No. H06-341515
In a conventional transfer arrangement for the four-wheel drive vehicle, e.g., the transfer for a part-time four-wheel drive (referred to as “4WD”) vehicle equipped with a switching system between “high” and “low” ranges, there are inconveniences described below when the system is equipped with the center differential to provide a full-time four-wheel drive position. (1) The transfer substantially increases in length, since the transfer comprises three parts, i.e., a switching part to switch between “high” and “low” ranges, a switching part between “2WD” and “4WD”, and a center differential. (2) When the switching part between “high” and “low” ranges is provided with planetary gears to avoid the increase in length of the transfer, the transfer becomes larger in a radial direction of input and output shafts, i.e., in a widthwise direction of the transfer (in other words, a “fat-body phenomenon”). A floor tunnel needs to extend its width, thereby narrowing the inner space.
In order to prevent this “fat-body phenomenon”, it is required that the switching part for switching between “high” and “low” ranges is comprised as a parallel shaft type, and this switching part and the center differential are effectively positioned to reduce overall length of the transfer.
For this reason, the purpose of this invention is to shrink the size of the transfer arrangement which converts the torque transmitted from the power source to the input shaft into high and low speeds and transmits to the center differential.
In order to obviate or at least minimize the above inconvenience, the present invention provides a transfer arrangement for a four-wheel drive vehicle having an input shaft into which the torque from the power source is transmitted, a transmission which converts the torque of the input shaft into high and low speeds, and a center differential aligned with the input shaft to distribute the torque output from the transmission into front and rear wheels of the vehicle. The transmission includes a first gear attached to the input shaft, a first counter gear attached to a countershaft in parallel with the input shaft to receive the rotation of the first gear, a second counter gear integrated to the countershaft and rotating therewith, and a second gear aligned with the input shaft and rotatably supported along the input shaft to receive the rotation of the second counter gear. High speed-side and low speed-side output parts are attached to the first and second gears respectively. The center differential is disposed between the high speed-side and low speed-side output parts. An engaging device is disposed adjacent to the center differential to selectively engage with the high speed-side and low speed-side output parts.
Accordingly, this configuration eliminates the space needed for the hub dedicated to the transmission and the connection shaft to connect the hub with the center differential, so that the axial length of the transfer arrangement becomes smaller.
The present invention will now be described in specific detail with reference to the accompanying drawings.